There is a related art apparatus which is configured to drive an object to be driven with a motor. The related art apparatus includes a position sensor for detecting the position of an object to be driven or the rotation position of a motor and is configured to perform position control and speed control of the motor on the basis of a position detection signal from the position sensor. One example of the related art apparatus is an ink jet printer which forms an image on paper while moving a carriage, which is mounted with a recording head, in a main scanning direction by a motor. Another example of the related art apparatus is a scanner which reads an image of a document while moving a line sensor for image reading in a sub-scanning direction by a motor.
As described above, for the related art apparatuses in which motor control using a position sensor is performed, there is a demand for improvement in the detection accuracy of the position sensor in order to perform motor control with high precision (eventually, in order to control the driving of an object to be driven with high precision).
In the case of controlling the position of a motor on the basis of a position detection result using an encoder, the accuracy of position detection depends on the resolution of the encoder. Accordingly, in order to improve the accuracy of motor control by performing the position detection with high precision, it is necessary to use an encoder with high resolution by reducing a distance between slits.
However, a method of improving the resolution of an encoder by reducing the distance between slits has practical limitations due to manufacturing problems and cost problems.
Therefore, as a method of improving the position detection accuracy of an encoder without improving an encoder wheel or a linear scale which forms the encoder, a method has been proposed in which the encoder slit distance is measured using a sufficiently high-speed clock compared with an interval of an encoder pulse and the position detection accuracy of the encoder is improved on the basis of the measurement result.